Method and apparatus for manufacturing apertured strip

ABSTRACT

An improvement in the process for manufacturing apertured strip can be achieved by stamping a metal strip at a pitch less than desired, advancing the strip to a pitch-sensing station, wherein the growth of the pitch is measured, indenting the carrier strip a sufficient amount to achieve the desired pitch. A subassembly is useful in the process comprising a stamping means for stamping at less than the ultimate desired pitch, a pitch-sensing means that measures the growth of the pitch spaced apart from said stamping die, an indenting means for indenting the carrier strips a sufficient amount to achieve desired pitch said indenting means being spaced apart from said pitch-sensing means and a cutting means for cutting said strip into predetermined lengths.

United States Patent [151 3,638,463

Cala Feb. 1, 1972 [54] METHOD AND APPARATUS FOR Primary Examiner-Charles W. Lanham MANUFACTURING APERTURED STRIP Assistant Examiner-R. M. Rogers tt N .l.OM ll ,D ldR.C tl dW" 721 inventor: Philip L. Cala, Jamestown, NY. ,1 {223 a ey as e [73] Assignee: Sylvania Electric Products Inc.

57 ABSTRACT [22] Filed: May 28, 1970 1 An improvement in the process for manufacturing apertured [21] Appl 41318 strip can be achieved by stamping a metal strip at a pitch less than desired, advancing the strip to a pitch-sensing station, [52] U.S.Cl ..72/l2,72/338, 83/251 wherein the growth of the pitch is measured, indenting the lllt- B211! 321d 3 /0 266 5/20 carrier strip a sufficient amount to achieve the desired pitch. [58] Field Of Search ..72/l0, 12, 330, 338; 83/251 A b ssembly is useful in the process comprising a stamping means for stamping at less than the ultimate desired pitch, a [56] References C'ted pitch-sensing means that measures the growth of the pitch UNITED STATES PATENTS spaced apart from said stamping die, an indenting means for indenting the carrier strips a sufficient amount to achieve 2,925,847 2/1960 Burns ..83/405 X desired pitch said indenting means being spaced apart from PUCCI said pitch sensing means and a cutting means for utting aid strip into predetermined lengths.

7 Claims, 3 Drawing Figures 3 l l l 3 2 CONTROL MEANS 36 O o 20 I2.

s /6 1 CI I4 r r 1 L I E 5 r321? i I I L i D Q 0 Z2 M i J 4 r1 /8 L Z9 PATENTEB FEB ma INVENTOR. PHILIP L. CALA ATTOZ N EY BACKGROUND OF THE INVENTION This invention relates to the manufacture of apertured strip solid metal strip. More particularly, it relates to a method and apparatus that enables the manufacture of apertured strip having more exact pitch between the individual adjacent stamped patterns.

In the production of apertured strip by stamping a series of patterns in a metal strip, there is a problem with maintaining proper pitch between the individual patterns. One of the methods of manufacture of items such as lead frames for integrated circuits is to stamp a series of patterns in a relatively thin metal strip. These patterns are individually stamped in a series from a continuously advancing metal strip. Parallel carrier strips extending the length of the strip and divider strips between the individual patterns provide the support for the series of patterns. Generally the strip is cut into segments containing a desired number of patterns such as 10. The amount of metal left to support the individual patterns is relatively small, therefore, as the stamped strip moves the pitch or distance between the same spot on the individual patterns tends to become larger because the thin metal tends to become thinner due to the forces that are exerted upon it while it is moving to the point where it is cut into segments. Several factors exist which causes the beforementioned growth to be nonuniform. For example, for different uses, different metals can be desired. Additionally different thicknesses of metal can be desired. Also, in any solid strip in which the patterns are stamped some variations in thickness or hardness occurs. It is desirable to use the same equipment regardless of the material being processed. Heretofore the die used to stamp the pattern was set to stamp in a set sequence to give the desired pitch and as can be appreciated due to the variation in growth the pitch was nonuniform in the finished product.

It is believed, therefore, that a method and apparatus that provides a finished product having a relatively more uniform pitch would be an advancement in the art.

OBJECTS AND SUMMARY OF THE INVENTION It is an object of this invention to provide a method for producing apertured strip having a series of stamped patterns having a relatively uniform pitch.

It is an additional object of this invention to provide apparatus in the form of a subassembly that can be used with conventional stamping equipment that enables the production of apertured striphaving a relatively uniform pitch between the individual patterns.

In accordance with one aspect of this invention there is provided an improvement in the process of continuously manufacturing segments of apertured metal strip having a series of individual patterns having a desired pitch from a solid, relatively thin metal strip wherein the apertured metal strip has two substantially parallel carrier strips running the length of the strip and on opposite sides thereof and divider strips between the individual adjacent patterns and extending between the carrier strip and wherein in the process the patterns are individually stamped in the metal. After stamping the strip is cut into relatively uniform segments containing a predetermined number of patterns. The improvement comprises stamping the strip in a series of patterns at a pitch less than the desired pitch, determining the pitch at point after stamping and before cutting into segments and indenting the carrier strips, at a point after determining the actual pitch and before cutting into segments a sufficient amount between the individual patterns to attain the desired pitch.

In accordance with an additional aspect of this invention, there is provided a subassembly to control the pitch between individual stamped adjacent patterns comprising a die for individually stamping adjacent patterns in a continuously advancing solid strip leaving carrier strips running the length of the strips, the pitch of adjacent patterns being less than the desired pitch, a means for measuring the pitch between adjacent patterns spaced apart from the die and a means for indenting the carrier strips between adjacent patterns to there by increase the pitch between adjacent patterns.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of one embodiment of the subassembly of this invention;

FIG. 2 is a plan view of one embodiment of the subassembly of this invention;

FIG. 3 is a cross-sectional view of the adjustable carrier strip-indenting means taken along 3-3 of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION For a better understanding of the present invention, together with other and further objects, advantages, and capa bilities thereof, reference is made to the following specification and appended claims in connection with the aforedescribed drawings.

In the manufacture of apertured strip having individually stamped adjacent patterns by the process of this invention, the patterns are stamped at a pitch less than that desired. In the manufacture of certain specific lead frames from Rodar metal having a thickness of 0.010 to 0.030 it is desirable to have a pitch of about 0.751 inch. In this invention the pitch as originally stamped is about 0.7506 inch. The average change in pitch on a metal strip of 0.0l0-inch thickness will generally average from about 0.0002 to about 0.0003 inch. Thus, at a point prior to cutting the actual pitch is determined which is normally less than the desired pitch. After the measurement is made and allowance is made for continued growth to the point where the strip will be cut into segments, the carrier strips are indented a sufficient amount to change the pitch a sufiicient amount so that at the time the segments are cut, the pitch in the segments will be 0.751. The amount of indentation is varied, depending upon the pitch measurement. For example, a segment containing 10 patterns, the pitch between the adjacent patterns before indentation can vary from 0.7506 to 0.7509 depending upon the variations in the thickness of the solid strip. The amount of indentation will, therefore, be dependent upon the actual individual pitch measurement between adjacent patterns. The thinness of the metal enables the slight indentations to cause the metal to flow thereby increasing the pitch between adjacent patterns. As can be appreciated, the amount of growth is dependent upon several factors such as the thickness of the metal and the composition of the metal. The method of this invention enables the continuous method of stamping to be more flexible and increases the accuracy of the pitch regardless of the variations in the metal used. In most instances, the depth of the indentation will be about equal to the growth in pitch.

As previously mentioned in the apertured strip there are dividing strips that separate the individual patterns and extend between the carrier strips. Since the metal is relatively thin and the dividing strips are narrow there is a tendency for the dividing strips to become bowed as the apertured strip advances. The indentation step also straightens out the camber that is present in the dividing strips in addition to obtaining the desired pitch. Generally only slight pressure, that is, less than the amount required to cause growth of pitch is required to satisfactorily adjust the camber on individual dividing strips.

To more fully describe the invention reference is made in detail to the drawings.

With particular reference to FIGS. 1 and 2 a solid metal strip 10 is stamped with the stamping means 12 to produce an apertured strip 14 having a first carrier strip 16 and a second carrier strip 18 with adjacent patterns 20 and 22. The pitch between the adjacent patterns after the stamping means I2 is less than desired. A pitch-measuring means 24 spaced apart from the stamping means 12 measures the growth in pitch due to the movement of the apertured strip M. In the embodiment shown an additional camber-measuring means 26 is also utilized. An adjustable carrier strip-indenting means 28 is spaced apart from the pitch-measuring means 24 and the cambermeasuring means 26. In the embodiment shown a signal is fed from the pitch-measuring means 24 to thecontrol means 30 and is transmitted to the two driving means 32 and 34 for the indenting means 28. Signals from the camber-measuring means 26 are also fed to the driving means 32 and 34. The driving means 32 and 34 provides a sufficient degree of indentations to the carrier strip 16 and 18 to achieve the desired pitch. The apertured strip is thereafter cut into predetermined lengths by the cutting means 36.

With particular reference to FIG. 3, one embodiment of an adjustable carrier strip-indenting means 28 is shown. The indenting means 28 comprises two indenters 38 and 40, a means 42 and 44 for adjusting the degree of indentation and a means 46 for applying pressure to the indenters 38 and 40 to produce the desired degree of indentation in the apertured strip 14 to achieve the desired pitch. Although the adjusting means as shown consisting of moving themembers 48 and 50 which in turn governs the amount of movement of the indenters 38 and 40, other means can be used and will occur to one skilled in the art. Additionally, although the embodiment illustrated herein shows automatic adjustment, in some instances this can be done manually.

While there have been shown and described what are at present considered the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

What is claimed is:

I. In the process of continuously manufacturing segments of apertured metal strips containing a series of individual patterns having a desired uniform pitch between adjacent patterns wherein in said process a solid metal strip is stamped in individual patterns with a first and second substantially parallel carrier strips extending the length of said strips and dividing strips between said individual patterns and extending between said first and second carrier strips and is thereafter cut into relatively uniform segments having a predetermined number of patterns in said segment the improvement comprising:

a. stamping said patterns at a pitch less than said desired pitch,

b. measuring the pitch between adjacent patterns at a point after stamping and prior to cutting said strip into said segments, and

c. indenting said carrier strip between adjacent patterns a sufficient amount to achieve desired pitch.

2. An improvement according to claim 1 wherein said solid metal strip has a thickness less than about 0.060 inch.

3. An improvement according to claim 2 wherein said depth of indentation is substantially equal to the growth in pitch due to said indentation.

4. An improvement according to claim 3 wherein said pat- .terns are lead frames for integrated circuits.

5. In a machine for producing segments of apertured metal strip having patterns in a desired pitch from a solid, relatively thin, continuously advancing metal strip by stamping individual patterns therein, the subassembly comprising:

a. a stamping means for stamping patterns in said strip at a pitch less than the desired pitch,

b. a pitch-measuring means spaced apart from said die,

c. an adjustable carrier strip-indenting means spaced apart from said pitch-measuring means, and

d. a means for cutting said apertured strip into segments.

6. A subassembly according to claim 5 wherein said pitchmeasuring means provides a signal to said indenting means to adjust the degree of indentation.

7. A subassembly according to claim 6 wherein a cambermeasuring means is provided between said stamping means and said carrier-indenting means. 

1. In the process of continuously manufacturing segments of apertured metal strips containing a series of individual patterns having a desired uniform pitch between adjacent patterns wherein in said process a solid metal strip is stamped in individual patterns with a first and second substantially parallel carrier strips extending the length of said strips and dividing strips between said individual patterns and extending between said first and second carrier strips and is thereafter cut into relatively uniform segments having a predetermined number of patterns in said segment the improvement comprising: a. stamping said patterns at a pitch less than said desired pitch, b. measuring the pitch between adjacent patterns at a point after stamping and prior to cutting said strip into said segments, and c. indenting said carrier strip between adjacenT patterns a sufficient amount to achieve desired pitch.
 2. An improvement according to claim 1 wherein said solid metal strip has a thickness less than about 0.060 inch.
 3. An improvement according to claim 2 wherein said depth of indentation is substantially equal to the growth in pitch due to said indentation.
 4. An improvement according to claim 3 wherein said patterns are lead frames for integrated circuits.
 5. In a machine for producing segments of apertured metal strip having patterns in a desired pitch from a solid, relatively thin, continuously advancing metal strip by stamping individual patterns therein, the subassembly comprising: a. a stamping means for stamping patterns in said strip at a pitch less than the desired pitch, b. a pitch-measuring means spaced apart from said die, c. an adjustable carrier strip-indenting means spaced apart from said pitch-measuring means, and d. a means for cutting said apertured strip into segments.
 6. A subassembly according to claim 5 wherein said pitch-measuring means provides a signal to said indenting means to adjust the degree of indentation.
 7. A subassembly according to claim 6 wherein a camber-measuring means is provided between said stamping means and said carrier-indenting means. 